Before Getting Started

There are plenty of questions you’ll have to ponder on to establish if your home project will fall under this rule.

  1. Will your planned expansion be on no more than 50% of the land surrounding your original home?
  2. If your extension is estimated to be in 2 meters of your property line, will your roofs overhang height be under 3 meters?
  3. Will your extension be smaller than the tallest area of your current roof and lower at the eaves than the existing?
  4. Will you be using materials that are the same or similar to the materials used for your existing home for your extension?
  5. Do you plan to avoid the usage of the following during your extension:
  • Veranda
  • Raised platform
  • Balcony
  • Chimney, flue, or vent pipe
  • A TV aerial or satellite dish

Answering yes to all of the prior questions mean you should read on to find out any further restrictions you may come across along your extension journey! If you’ve answered no, please read the restrictions section.

Single Story Rear Extensions

These extensions typically have minimal planning permission paperwork incorporated in the process, and normally planning permissions are not necessary at all. Single story rear extensions must not extend beyond the original rear wall of your home by more than 3 meters (9.84 feet) if you have a semi-detached house or 4 meters (13.12 feet) for a detached house. The maximum height of a single-story rear extension should not exceed 4 meters to avoid needing planning permission for the extension.

Living in a protected area such as an AONB (Area of Outstanding National Beauty), or a national park, will require prior approval, but the maximum size for your single-story rear extension can increase to 8 meters for detached homes and 6 meters for others.

However, prior approval is necessary for sizeable projects. To get prior permission, you must inform the council that you plan on extending your home. From there, the council member will consult your neighbors to ensure they have no objections, as changing your home affects the entire neighborhood’s value. If someone objects, the planning authority from your area will determine if you can proceed with your extension after weighing the effects of the neighboring properties.

Single Story Side Extensions

When organizing a single-story side extension, there are numerous things to consider. Side extensions must be single-story with a maximum height of 4 meters and have a width no more than half that of your original home. More than likely, you can build your single-story side extension without planning permission or prior approval, assuming you abide by the guidelines. The permitted development rights are not applicable to properties located on protected land such as AONB or national parks.

Multi Story Extensions

Under certain circumstances, you may be allowed to build multi-story extensions using the PDR rule. However, the rules are typically stricter than a single-story extension. The guidelines for multi-story extensions are as follows:

  • The multi-story extension can not pass the back of the original home by over 3 meters.
  • The multi-story extension can not be within 7 meters of any boundary opposite of the back wall of the house.
  • The roof pitch of your new home must match the current roof.
  • All upper-floor windows located in ‘side elevation’ must be obscure-glazed.

You should also be aware that multi-story side extensions are never allowed through the PDR rule and will always need planning permission regardless of the project.

Conservation Areas

When living on protected land such as Article2(3) designed land, certain aspects of the PDR rule won’t pertain to you. For example, all side extensions in protected land need planning permission no matter how large or small the extension.

For rear extensions, the PDR rule does not allow the cladding of exterior walls. It does not grant back-end expansions greater than one story without planning permission.


There are a lot of restrictions and rules that determine whether or not your extension will need planning permission.

  • The size of the extension can be no more than half of the land around the house from the time it initially was built. Consider whether any previous owners have carried out any extension work before you begin building.
  • No extension can pass under the permitted development rule if the extension, once finished, is closer to the public highway from either front elevation or side. If this is the case, you will be required to get permission before proceeding with your expansion.
  • No extension can be higher than the highest part of your roof. If you intend on making your extension taller than the highest part of your roof, you will need to get permission before proceeding.
  • Materials used in the extension should be similar, if not the same, to the materials already existing on the home. If you intend to use different materials, you will have to get prior permission.

Finding Quotes

Once you’ve determined your extension abides by the rules from the permitted development rights rule, you can start building! To find free extension quotes in as little as three steps, consider visiting Extension Prices. It’s as simple as

1 Explaining your project

They provide quotes for all types of home extensions!

2 Providing your address

Providing your address allows them to find reputable suppliers near you!

3 Receiving reduced cost installation

Compare quotes for a reduced cost extension that could save you £1,000’s!

How much for a small extension? Find out more here. Alternatively, if you have a garage and are thinking of adding a second story extension to your home, find out the cost of extending over a garage.

Mike Alexander
Hey there, I'm Mike - writer and part time home improvement expert at Refurbb. Since owning and refurbishing my own property in 2018, I've since been developing rental properties, writing about my home improvement endeavours, sharing what I've learned and connecting readers to reputable tradespeople in the UK.

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